In case of proximity contactless chip cards (for example radio frequency identification (RFID)—transponders) energy as well as information is transferred over an inductively coupled antenna interface. Information from a so-called reader (PCD—proximity coupling device) to a chip card or a transponder (PICC—proximity integrated circuit card) is typically transferred by amplitude modulations and by load modulations in the other direction from the PICC to the PCD. The communication for the 13.56 MHz ISO 14443 standard is defined by A/B/C/standards.
By using the type A Standard, amplitude modulation with a modulation index of up to 100% is used. A single bit is coded as a field pause. During the pause, the field emitted by the PCD antenna is reduced by the modulation index. With a modulation index of 100%, the field emitted by the PCD antenna is turned off during a type A pause. A 100% type A pause can last several microseconds. As the emitted field of the PCD antenna is also used to transfer energy to the PICC, the PICC is not supplied with energy during this time interval.
Therefore an energy reservoir (for example, a capacitor) is sometimes added to the PICC, to provide the amount of energy consumed by the PICC circuitry during the abovementioned type A gap or type A pause or field pause.
As the capacitor which is used, or even required in some cases, for surviving the longest type A gap possible (which is defined in the ISO 14443 Standard) is quite large, this capacitor significantly increases the area of the analog frontend of the contactless chip card or RFID transponder.
There is a desire in the art for providing a concept, which allows for a more efficient implementation of a power supply for transponders.